A polyethylene composition, its preparation method and application

Abstract

The present invention relates to a polyethylene composition, a preparation method and an application thereof, comprising: high-density polyethylene, ethylene-vinyl acetate copolymer EVA, EVA-g-NBR, flaky aluminum hydroxide, montmorillonite, silane coupling agent, initiator, antioxidant. The selected raw materials and formula combination of this patent not only have good mechanical and flame retardant properties, but also have excellent oil resistance effect, and are very suitable for use in cables that are in long-term contact with alkane oil substances.

Description

Technical Field

[0001] The invention belongs to the field of cable materials, and particularly relates to a polyethylene composition and a preparation method and application thereof. Background Art

[0002] Low smoke halogen-free polyolefin cross-linked insulation materials are usually made of a series of polyolefin resins such as PE / EVA / POE, and in order to meet the characteristics of low smoke and halogen-free, they are often filled with a large amount of hydroxide flame retardants to meet the flame retardant performance required by the standard. For special cables under complex working conditions, their working environment is often faced with various fuels and mineral oils. Since ordinary polyolefin materials have poor oil resistance and the density of the material is destroyed after adding a large amount of non-polar fillers, they are more susceptible to oil liquid infiltration and cause cable failure. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a high temperature oil resistant, low smoke halogen-free polyethylene composition and a preparation method and application thereof.

[0004] A polyethylene composition of the present invention comprises, by weight:

[0005]

[0006] The density of high-density polyethylene is not less than 0.960g / cm 3 The diameter-to-thickness ratio of the flaky aluminum hydroxide is ≥50. The density test is in accordance with GB / T 1033.1-2008; the diameter-to-thickness ratio test is in accordance with JC / T 2063-2011.

[0007] Preferably, the density of the high-density polyethylene is 0.961-0.970 g / cm 3 .

[0008] Preferably, the mass percentage of EVA in the EVA-g-NBR is 60-90%. Within this content range, the hardness of EVA is moderate and it has good blending compatibility with the material matrix resin. Too low EVA content is not conducive to the dispersion of the grafted material, and too high EVA content has no effect on its oil resistance.

[0009] Further preferably, the mass percentage of EVA in the EVA-g-NBR is 70-80%.

[0010] Furthermore, the preparation method of EVA-g-NBR includes: uniformly mixing EVA and NBR according to a weight ratio, refining at 110°C-130°C, then adding DCP, sulfur and zinc oxide, continuing to refine at a temperature of 120°C-130°C, extruding the refined mixture at a temperature of 150-170°C in a twin-screw extruder, and pelletizing to obtain EVA-g-NBR.

[0011] The mass percentage dosages of the DCP, sulfur, and zinc oxide relative to the total mass of EVA and NBR are respectively: DCP: 0.3 - 0.6%; sulfur: 0.8 - 1.2%; zinc oxide: 0.3 - 0.6%.

[0012] Preferably, the aspect ratio of the flaky aluminum hydroxide is 51 - 100. If the aspect ratio is too low, it cannot play the role of anti - oil penetration. If it is too high, the lamellar structure will be fragile, and it is prone to deformation and rupture during processing, resulting in a decrease in the anti - oil effect.

[0013] Preferably, the mass ratio of the flaky aluminum hydroxide to montmorillonite is (10 - 18):1.

[0014] The silane coupling agent is at least one of γ - aminopropyltriethoxysilane and triacetoxyvinylsilane; the initiator is an irradiation initiator; the irradiation initiator is one or more of TAIC, TMPTMA, and TMPTA.

[0015] Preferably, the antioxidant is one or more of hindered phenol antioxidants (such as antioxidant 1010, antioxidant 1790, 3114), phosphite antioxidants (antioxidant 168, antioxidant 686, PEP - 36), and thioether antioxidants (such as DSTDP, DLTDP, IRGANOX PS802 FD).

[0016] Preferably, by weight parts, the components include:

[0017]

[0018] A preparation method of the polyethylene composition of the present invention includes:

[0019] Weigh each component according to the weight ratio, mix them, and then carry out internal mixing by an internal mixer and extrude and pelletize through a two - stage single - screw extruder to obtain the polyethylene composition.

[0020] Preferably, the temperature of the internal mixer is controlled at 130 - 140°C, and the temperature of the single - screw extruder is controlled at 140 - 160°C.

[0021] An application of the polyethylene composition of the present invention in cable materials, such as mainly applied to working occasions with a heavy oil - contaminated environment, such as locomotive cables and marine cables.

[0022] Principle: 1. Ultra-high density polyethylene has an ultra-high degree of crystallinity and good oil resistance. 2. NBR is a strongly polar rubber with good oil resistance itself, but has poor compatibility with PE and EVA resins. In this patent, NBR is first chemically grafted with EVA, so that the grafted product has some oil resistance properties of NBR and good compatibility with EVA resin, and will not cause adverse effects such as poor oil resistance and mechanical properties caused by phase separation. 3. Magnesium hydroxide with a relatively large aspect ratio is selected, which has better liquid barrier properties, and its compounding with exfoliated montmorillonite has a good synergistic oil resistance effect.

[0023] Beneficial effects

[0024] The raw materials and formula combination selected in this patent not only have good mechanical and flame retardant properties, but also have excellent oil resistance, and are very suitable for use in cables that are in long-term contact with alkane oil substances. Specific embodiments

[0025] The following further elaborates the present invention in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of this application.

[0026] I. Raw material components

[0027] High density polyethylene - 1: Dow Chemical, ELITE AT 6900, density 0.961 g / cm 3 ;

[0028] High density polyethylene - 2: American Amco, HDPE 006964EG, density 0.965 g / cm 3 ;

[0029] High density polyethylene - 3: Sinopec, HDPE HHM5502LW, density 0.955 g / cm 3 ;

[0030] Ethylene - vinyl acetate copolymer EVA: Dow of the United States, EVA FL00328;

[0031] NBR: Nitrile rubber: Ningbo Shunze, NBR3355;

[0032] EVA - g - NBR - 1: The mass percentage of EVA is 80%;

[0033] EVA - g - NBR - 2: The mass percentage of EVA is 70%;

[0034] EVA-g-NBR-3: The mass percentage of EVA is 60%;

[0035] EVA-g-NBR-4: The mass percentage of EVA is 90%;

[0036] Preparation method of EVA-g-NBR: Mix EVA and NBR evenly according to the weight ratio (for No. 1-4, EVA: 80, 70, 60, 90 parts respectively, NBR: 20, 30, 40, 10 parts respectively), knead at 110 °C, then add 0.5 part of DCP, 1 part of sulfur, and 0.5 part of zinc oxide, continuously knead at a temperature of 120 °C, extrude and pelletize the kneaded mixture at 170 °C in a twin-screw extruder to obtain EVA-g-NBR.

[0037] Flaky aluminum hydroxide-1: Aspect ratio 100: CHAMPION MARTINAL ON-310, USA

[0038] Flaky aluminum hydroxide-2: Aspect ratio 55: CHAMPION MARTINAL ON-903, USA

[0039] Flaky aluminum hydroxide-3: Aspect ratio 150: ALBEMARLE, TS-610

[0040] Flaky aluminum hydroxide-4: Aspect ratio 30: ALBEMARLE, OL-104

[0041] Montmorillonite: DK-1; Zhejiang Fenghong

[0042] Silane coupling agent: (γ-aminopropyltriethoxysilane): KH-550, Jiangsu Guigang;

[0043] Irradiation initiator: TAIC; commercially available;

[0044] Antioxidant: Hindered phenol antioxidant 3114, phosphite antioxidant PEP-36 and thioether antioxidant IRGANOX PS 802FD with a mass ratio of 1:1:1.

[0045] II. Preparation methods of examples and comparative examples

[0046] Weigh each component by weight and put them into a kneader. After kneading by the kneader, extrude and pelletize through a two-stage single-screw extruder. The temperature of the kneader is controlled at 130-140 °C, and the temperature of the single-screw extruder is controlled at 140-160 °C.

[0047] III. Test standards and methods

[0048] The obtained polyethylene composition was pressed into a sheet on a flat vulcanizer at 180 °C for 10 min under a pressure of 15 Mpa. The thickness of the sample sheet was 1 mm. After being placed at room temperature for 16 h, it was irradiated with high-energy electron beam at an irradiation dose of 15 Mrad. The irradiated sample sheet was tested as follows:

[0049] Tensile strength before oil immersion: GBT 1040.2-2018

[0050] Elongation at break before oil immersion: Refer to the standard GBT 1040.2-2018.

[0051] Oil resistance test: The sample strip was immersed in 902# mineral oil at 70 °C for 168 h, and then the tensile strength and elongation at break of the material after oil immersion were tested;

[0052] Retention rate of tensile strength after oil resistance = (tensile strength after oil immersion / tensile strength before oil immersion) * 100%;

[0053] Retention rate of elongation at break after oil resistance = (elongation at break after oil immersion / elongation at break before oil immersion) * 100%;

[0054] Flame retardant grade test: Tested according to the test method of low-smoke and halogen-free material standard GB / T 32129-2015.

[0055] Table 1 Formulation ratio (parts by weight) of the examples

[0056]

[0057] Table 2 Formulation ratio (parts by weight) of the comparative examples

[0058]

[0059]

[0060] Table 3 shows the performance effect data of the examples

[0061]

[0062] Table 4 shows the performance effect data of the comparative examples

[0063] Comparative example 1 Comparative example 2 Comparative example 3 Comparative example 4 Comparative example 5 Comparative example 6 Tensile strength before oil immersion (Mpa) 13.2 14.1 10.5 14.4 13.5 13.8 Elongation at break before oil immersion (%) 200 190 110 220 180 200 Retention rate of tensile strength after oil immersion (%) 73 60 64 52 62 57 Retention rate of elongation at break after oil immersion (%) 75 51 58 66 65 61 Flame retardancy B1 B1 B1 B2 B2 B2

[0064] Analysis and description: The tensile strength of the full formula of the embodiments of the present invention is greater than 14 Mpa, the elongation rate is above 220%, and the retention rate of the tensile strength / elongation rate after soaking in oil is greater than 80%. The flame retardant level reaches B1 level, indicating that the material has excellent conventional mechanical properties, excellent oil resistance at 70 °C high temperature, and good flame retardant properties. The density of the high-density polyethylene in Comparative Example 1 is relatively low, and its oil resistance is poorer and the strength is lower compared with Example 1; the aspect ratio of the aluminum hydroxide in Comparative Example 2 does not meet the requirements of this patent, resulting in a significant reduction in oil resistance. Although NBR is introduced in Comparative Example 3, it is not effectively compatibilized with the matrix resin, resulting in very poor conventional mechanical properties and low oil resistance; in Comparative Example 4, without montmorillonite, it is impossible to form a synergistic effect with flaky aluminum hydroxide, and its oil resistance is extremely poor; in Comparative Examples 5 and 6, only one inorganic filler is added, and these two comparative examples also cannot form a good synergistic effect. Not only can the flame retardant grade only reach B2 level, but also the oil resistance effect is greatly reduced.

Claims

1. A polyethylene composition, characterized in that, By weight parts, the components include: wherein the density of the high-density polyethylene is not less than 0.960 g / cm 3 ; the aspect ratio of the flaky aluminum hydroxide satisfies 150 ≥ aspect ratio ≥ 50; the mass percentage of EVA in the EVA-g-NBR is 60-90%.

2. The polyethylene composition according to claim 1, wherein The aspect ratio of the flaky aluminum hydroxide is 51 - 100.

3. The polyethylene composition according to claim 1, wherein The mass ratio of the flaky aluminum hydroxide to montmorillonite is (10 - 18):

1.

4. The polyethylene composition according to claim 1, wherein The silane coupling agent is at least one of γ-aminopropyltriethoxysilane and triacetoxyvinylsilane; the initiator is an irradiation initiator; the irradiation initiator is one or several of TAIC, TMPTMA, and TMPTA.

5. The polyethylene composition according to claim 1, characterized in that, The antioxidant is one or several of hindered phenol antioxidants, phosphite antioxidants, and thioether antioxidants.

6. The polyethylene composition according to claim 1, characterized in that, By weight parts, the components include:

7. A method for preparing the polyethylene composition according to claim 1, comprising: Weigh each component according to the weight ratio, mix them, and then carry out kneading through a kneader and extrude and pelletize through a two-stage single-screw extruder to obtain the polyethylene composition.

8. The preparation method according to claim 7, wherein, The temperature of the kneader is controlled at 130 - 140 °C, and the temperature of the single-screw extruder is controlled at 140 - 160 °C.

9. An application of the polyethylene composition according to any one of claims 1 - 6 in cable materials.

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